For the synthetic production of sounds of a predetermined timbre two methods are chiefly or significance, which are based on different initial assumptions:
(a) The part tone structure of the desired sound is composed from individual sinusoidal part components; or PA1 (b) the part tones of the desired sound are taken from sounds or noises by filtration, which comprise the required part tones in a sufficient number and with a sufficient volume.
Sounds as can be produced for example with musical instruments, have in the stationary case spectra of purely harmonic spectral components. Such sounds can therefore only be produced by the above mentioned methods and cannot be produced by modulating methods for sound synthesis, which lead to non-harmonic spectra but these spectra however are of significance for choral effects, finely modulated events and attack and decay events. The natural character of the sounds of musical instruments and the like is therefore determined by a quasi-stationary sound development (harmonic spectrum) with "timbre modulation" (Meyer-Eppler 1949) and noise fractions.
The phase position of the part tones is generally not taken into account in synthetic sound production. In the case (a) it is difficult to monitor and in case (b) it represents a secondary accompanying phenomena of sound or noise productions, which is taken as a basis (for example delta pulse, saw-tooth) and of the following filter networks.
If in sound synthesis SCHUMANN'S Timbres Laws are to be taken into account, something which is necessary in order to obtain the best possible representation of natural sounds, the spectral enveloping curve must be precisely controlled for part tone synthesis or filtering, something which involves substantial problems.
Accordingly one aim of the present invention is that of providing a new method and new devices for synthetic electronic sound production, in the case of which formant formation, SCHUMANN'S Timbres Laws and also the quasi-stationary sound development can be easily controlled and at the same time the correct phase relationships can be maintained between the part tones.
These and further aims are to be attained by the invention.
While a German Patent Specification (Patentschrift No. 1,902,376) refers to a generator for the simultaneous production of tones of a musical scale which is preferably completely tempered, in the case of which the signals for the different tones consist respectively of pulse sequences, which comprise all pulses of one duration, the pulses of the pulse sequences for two different tones however form different pulse patterns, and since the pulses are not regularly distributed in the pulse series, it is not possible to use the pulse series directly as tone signals, since a tone produced from such a pulse series makes a very unpleasant impression on the ear.